Self-launching movable scaffolding system

ABSTRACT

A self-launching movable scaffolding system comprising: a main girder which transfers loads to supports; a front nose which transfers load of the system to support during launching; a rear nose which transfers load to a rear support during casting and launching, which is equipped with a rail system; hanger trusses which transfer load from a formwork to the main girder during casting; a rear support which provides support to the system during rebar cage installation, casting, and launching; a front support which provides support to the system during rebar cage installation and casting; a front and a middle launching support which provide support to the system during launching; a launching wagon for providing support and movement of the system; a trolley system which provides relocation to the front and middle launching supports and provides rebar cage delivery; and a formwork which is a mold for forming concrete to a shape.

TECHNICAL FIELD

Construction Engineering

BACKGROUND ART

Bridge construction especially for a whole span cast in-situ concretebridge, over deep valleys, water crossings with steep slopes, overhighway or railway, or environmentally protected regions can offer manychallenges. The Movable Scaffolding System (MSS) for bridge constructionmay offer advantages over conventional construction (ConventionalScaffolding), including creating minimal disturbance to surroundings,providing a more concentrated work area for superstructure assembly, andpossibly increased worker safety given the improved erectionenvironment.

Conventional Scaffolding or Formwork was formerly built in place, usedonce and wrecked. Because of high labor cost and material costs, thetrend today is toward increasing prefabrication, assembly in largeunits, erection by mechanical means such as “movable forms” andcontinuing modify and reuse the forms for other projects.

Movable Scaffolding Systems are conceived to be used in the constructionof cast in-situ concrete bridges and they are travelling steelstructures supporting the formwork that gives shape to the bridge. TheMSS is built to be backed off from the hardened concrete, moved to a newposition, and precisely adjusted for concreting the next span.

The Movable Scaffolding System was developed in the mid 1970's. Thesystem has since been further developed and has become a very popularsystem for constructing bridges worldwide. The ability to adapt the MSSto different cross sections allows the contractor to use the equipmentfor different projects elsewhere.

MSS System

The MSS consists of a support structure spanning between two piers fromwhich formwork is either supported or suspended. The inner formwork(core form) is collapsible and can run on a rail system to allow easyrelocation to the next span. The system is designed so that the outerformwork can be opened sufficiently to allow it to pass around thebridge columns during the launching process. After launching theformwork is closed again and after setting to the correct alignment,placement of reinforcement can start.

Type of MSS

The MSS can be divided into two types, namely, (i) underlane (orunderslung) and (ii) overlane (or overhead). The underlane type of MSShas two parallel girders. which supports the formwork. The overlane typeof MSS has one or two main girders from which the formwork is suspended.

The choice of which type to be used depends on site conditions such asheight restrictions, type of bridge deck (e.g. single cell, twin cell,double T) and height of columns.

The Self-Launching MSS

NRS is the first in the world to develop the Self-launching MSS (SL-MSS)in order to to solve the problems related to the difficulties inhandling pier support brackets over water as well as on high piers. Thissystem is able to transfer forward and mount the pier support bracketswithout any need of an independent crane. The SL-MSS has beensuccessfully used in the construction of several major bridge projectsworldwide and is widely sought after due to its cost and operationalefficiency.

However, the existing problems related to current MSS includerequirement of long cycle time, inability to deliverable whole rebarcage simultaneously or all at once, requirement of several block-outs inthe superstructure, requirement of hanging bars passing through thesuperstructure deck to support the formwork, requirement of otherequipments necessary for relocation of the supports and, last but notleast, the complexity of its operation as well as the labor intensivework.

Moreover, most of the movable scaffolding systems at present havelimitations in their operation regarding the high costs of constructionmanpower and the cost of assembling, dissembling and re-assembling.

This invention provides the new MSS with the self-launching system usedfor cast-in-situ bridges which can offer many cost-saving advantages tothe bridge construction project.

BRIEF DESCRIPTION OF DRAWING

FIGS. 1-A and 1-B show General Arrangement: Elevation and Plan

FIGS. 2-A and 2-B show Section A at Hanger Truss: Rebar cageinstallation & Concrete positions

FIGS. 3-A and 3-B show Section A at Hanger Truss: Launching position attypical pier & portal pier

FIGS. 4-A, 4-B and 4-C Section B at Rear Support: Rebar cageinstallation, concreting and launching positions

FIGS. 5-A and 5-B show Section C at Front support: Rebar cageinstallation and concreting positions

FIGS. 6-A and 6-B show Section C at Front support: Launching position attypical pier & portal pier

FIGS. 7-A and 7-B show Section D at Middle launching support: Launchingand relocating positions

FIGS. 8-A and 8-B show Section E at Front launching support: Launchingand relocating positions

FIGS. 9-A and 9-B show Launching sequence: Stage 1 and 2

FIGS. 10-A and 10-B show Launching sequence: Stage 3 and 4

DISCLOSURE OF THE INVENTION

The self-launching movable scaffolding system (SL-MSS) according to thisinvention comprises of

-   -   Rear Nose (120), as shown in FIG. 1-A, which provides a transfer        of load to Rear support (400) during casting and launching is        equipped with the mono-rail (701) for electrical lifting hoist        (702) used for rebar cage (900) loading.    -   Hanger Trusses (200) which provides a transfer of load from        formwork (800) to main girder (100) during casting. There is the        second folding function on the upper part of the said hanger        trusses (200) which creates the wider opening and the higher        position as shown in FIG. 3-B. This will allow the MSS to pass        the portal pier area (416) or other obstructions.    -   Rear Support (400) which provides support to the MSS during        rebar cage (900) installation, casting, and launching. The said        rear support (400) can be opened in the center for rebar cage        (900) to pass through as shown in FIG. 4-A and unlike the other        previous systems that require the additional rear support for        casting, the said Rear support (400) of this invention is now        designed to take the casting load. The foldable legs (401),        parts of the Rear support (400), are folded up to support        directly to the main girder (100) during casting and launching.        As shown in FIG. 4-B, Rear support (400) is set for casting        stage. The rear support main jacks (402) are activated and        transferred load to existing bridge. During MSS launching as        shown in FIG. 4-C, The rear support main jacks (402) are        deactivated and load is transferred pass through the express        rollers (403) to the existing bridge. There are rear support        side shifting cylinders (404) equipped at top of the rear        support (400) and the main girder (100). They are used for        transverse adjusting of the main girder during launching pass        through curve spans and for transverse adjusting of the rear        support (400) itself before casting. The said Rear Support (400)        is fixed to the main girder (100). No other external equipment        is required for its relocation.    -   Front Support (410) which provides support to the MSS during        rebar cage (900) installation and casting. As shown in FIG. 5-A,        The said Front support (410) is opened at the center for rebar        cage (900) to pass through. Once finish placing the rebar cage        (900), tension bars (415) are installed and engaged to the front        support (410) as shown in FIG. 5-B to confine the deflection of        the front support (410) during casting stage. Unlike the other        previous systems that require the block-outs in bridge        structure, there is no any part of the Front support (410) pass        through the bridge structure. Therefore, block-outs are not        required.    -    During casting, the front support main jacks (413) are        activated and transferred load from main girder (100) to the        front support (410). The Front support legs (412) which are        parts of the front support (410) provide a transfer of load        further to column footing. There are front support side shifting        cylinders (414) as shown in FIG. 5-B equipped at top of the        front support (410) and the main girder (100) to allow the        transverse adjusting of the main girder. As shown in FIG. 6-A,        the locking arms (411) at the lower part can be opened to pass        the pier during launching. The Lower parts of the front support        (410) as shown in FIG. 6-B can be disconnected when launching        pass the portal area (416). The said front support (410) is        fixed to the main girder (100). No other external equipment is        required for its relocation.    -   Front Launching Support (420) provides support to the MSS during        launching operation.    -    The said front launching support (420) is set and secured on        the pier top (425) as shown in FIG. 8-A with the launching wagon        (500) at top which allows the front nose (110) and the main        girder (100) to glide or move over to the new set position. The        said front launching support (420) can be dissembled from pier        and suspended to front nose (110) as shown in FIG. 8-B in order        to relocate to the next pier.    -   Middle Launching Support (430) provides support to the MSS        during launching operation. The said middle launching support        (430) is suspended to the front nose (110) as shown in FIG. 1-A        during casting. The said middle launching support (430) is moved        back and set on already cast concrete, as shown in the dotted        line in FIG. 1-A , and activated to support the MSS during        launching. The cross section FIG. 7-A and 7-B show the middle        launching support (430) in active and inactive stages        respectively.    -   Trolley system (700) provides relocation to the said Middle        lunching support (430) and the said Front launching support        (420) and also provides the rebar cage (900) delivery. The said        trolley system is composed of the mono-rail (701) set along the        rear nose (120), main girder (100), and front nose (110) and the        electrical lifting hoist (702).    -   Formwork (800) which is supported by formwork support frame        (801) according to this invention does not require hanging bars        for its hanging. Therefore, there is no obstruction during the        rebar cage (900) installation and concreting, refer to FIGS. 2-A        and 2-B.

In order to operate the said SL-MSS, the assembling and erectingsequence of the said SL-MSS can be described as the following:

-   -   1. Install the temporary tower (501) at the front pier of the        span being cast.    -   2. Install and secure the middle launching support (430) over        the temporary concrete foundation behind the abutment (417).    -   3. Assembly the main girder (100) on ground.    -   4. Install the said main girder (100) on to the said temporary        tower (501) and the said middle launching support (430).    -   5. Install the front support (410) and front support legs (412),        and rear support (400) to the said main girder (100). Activate        both supports to take load.    -   6. Remove the said temporary tower (501) and the said middle        launching support (430).    -   7. Install the hanger trusses (200) to the said main girder        (100).    -   8. Install formwork support frame (801) and formwork (800) on        hanger trusses (200).    -   9. Assembly the front nose (110) on ground. Install the said        front nose (110) to the said main girder (100).    -   10. Install trolley system (700).    -   11. Install other miscellaneous parts i.e. hydraulics equipment,        pumps, working platform to complete.

The launching sequence of the said SL-MSS comprises of the concretingand launching stages as the following:

Stage 1 (as shown in FIG. 9A)

-   -   1.1 MSS is set at the concreting position.    -   1.2 Front support (410) and rear support (400) are activated.    -   1.3 Middle launching support (430) is suspended to the front        nose (110).    -   1.4 Front launching support (420) is ready set on top of the        next pier.    -   1.5 Install rebar cage (900) and cast the span.

Stage 2 (as shown in FIG. 9B)

-   -   2.1 Move back and install the middle launching support (430) on        the already cast deck.    -   2.2 Release the main jacks (413 and 402) at front support (410)        and rear support (400) respectively. Rear support (400) is now        on the express rollers (403).    -   2.3 MSS is supported by middle launching support (430) and rear        support (400).    -   2.4 Open the hanger trusses (200).    -   2.5 Prepare for launching forward to the next span.

Stage 3 (as shown in FIG. 10A)

-   -   3.1 Launch forward the MSS to the new span until the front        support (410) is in same line with the front launching support        (420). During launching, the MSS is supported by front launching        support (420), middle launching support (430) and rear support        (400).    -   3.2 Activate the main jacks (413 and 402) at front and rear        supports (410 and 400) to take load of the MSS. Middle launching        support (430) and front launching support (420) are now free.

Stage 4 (as shown FIG. 10B)

-   -   4.1 Relocate the front launching support (420) to set on the        next pier.    -   4.2 Relocate the middle launching support (430) to suspend to        the front nose (110).    -   4.3 Close up the hanger trusses (200). Prepare the MSS for the        casting.    -   4.4 Repeat the stage 1-4 to complete the cycle for the next        span.

The dismantling process of the said SL-MSS can be described as thefollowing; Process of this operation is depended on the actual conditionat site and varied from job to job. A careful planning and drawingsshould be done before actual dismantling begins.

The general steps to dismantle the MSS after the last span has beencompleted are as follows:

-   -   1. Install temporary tower (501) at rear of main girder (100) to        take load of MSS.    -   2. MSS is supported by temporary tower (501) at the rear and the        middle launching support (430) at the front.    -   3. Dismantle the front nose (110) and front launching support        (420).    -   4. Fold down the bottom hangers (200) & start dismantling the        formworks (800) and formwork support frame (801).    -   5. Dismantle the hanger trusses (200).    -   6. Dismantle the front support (410) and front support leg        (412).    -   7. Dismantle the rear support (400).    -   8. Bring down the main girder (100) and dismantle each module.    -   9. Dismantle the middle launching support (430) and the        temporary tower (501).

The advantages of the movable scaffolding system when compared toconventional scaffolding or launching gantries are as the following

-   -   High efficiency in achieving rapid cycles    -   Lightweight    -   Easy to assemble    -   Reduce manpower    -   Can be adapted to different cross sections (allowing reuse        elsewhere)    -   High resistance to torsion    -   Maximum deflection=L/400 of span    -   Self launching option (no cranes required for pier bracket        relocation)    -   Limited interference to road users below during construction (if        applicable)    -   Pre-stress cost reduction (up to 30%) by reduction of deck        pre-stressing amount (no cantilever moments) or reduction in        number of anchorages & couplers in the pre-stressing of the deck        and reduction in amount of pre-stressing operations in the deck    -   Reduction in number of high risk operations (movements &        launching)    -   Easier geometry control (span by span construction)    -   No requirement for scaffolding to support the structure    -   Prefabricated rebar cage can be lifted and placed by MSS        -   Less forces in piers        -   No requirement for segmental casting yard and associated            transport costs.

1. A self-launching movable scaffolding system comprising: a main girderwhich transfer loads to supports; a front nose which is an extensionpart of the main girder located at a front end of the main girder andused to transfer load of the scaffolding system to support duringlaunching; a rear nose which provides a transfer of load to a rearsupport during casting and launching wherein the rear nose is equippedwith a rail system for a rebar cage delivery and support relocation by atrolley system; hanger trusses which provide a transfer of load from aformwork to the main girder during casting wherein the hanger trusseshave a second folding function on an upper part which creates a wideropening and a higher position for allowing the scaffolding system topass a portal pier area or other obstructions; a rear support whichprovides support to the scaffolding system during rebar cageinstallation, casting, and launching; a front support which providessupport to the scaffolding system during rebar cage installation andcasting; a front launching support which provides support to thescaffolding system during launching; a middle launching support whichprovides support to the scaffolding system during launching wherein themiddle launching support can be suspended to the front nose duringcasting; a launching wagon for providing support of the scaffoldingsystem which allows the scaffolding system to move both forward andbackward and further allows the scaffolding system to adjust sideways; atrolley system which provides relocation to the middle launching supportand the front launching support and further provides the rebar cagedelivery; and a formwork which is a mold for forming concrete to ashape.
 2. The self-launching movable scaffolding system according toclaim 1 wherein the rear support which provides support to thescaffolding system during rebar cage installation, casting, andlaunching can be opened at a center for the rebar cage to pass through.3. The self-launching movable scaffolding system according to claim 1wherein the front support which provides support to the scaffoldingsystem during rebar cage installation and casting can be opened at acenter for the rebar cage to pass through.
 4. The self-launching movablescaffolding system according to claim 1 wherein the formwork issupported by a formwork support frame with no hanging bars for itshanging.
 5. The self-launching movable scaffolding system according toclaim 1 further comprising rear support main jacks which are activatedand deactivated in order to transfer load to an existing bridge and passload through express rollers to the existing bridge, respectively. 6.The self-launching movable scaffolding system according to claim 1further comprising rear support side shifting cylinders which areequipped at a top of the rear support and the main girder, used fortransverse adjusting of the main girder during launching to pass throughcurve spans and for transverse adjusting of the rear support itselfbefore casting.
 7. The self-launching movable scaffolding systemaccording to claim 1 wherein: the front launching support is set andsecured on a pier top with the launching wagon at the top which allowsthe front nose and the main girder to glide or move over to a new setposition; and the front launching support can be dissembled from a pierand suspended to the front nose in order to relocate to a next pier. 8.The self-launching movable scaffolding system according to claim 1further comprising tension bars which are installed and engaged to thefront support in order to confine a deflection of the front supportduring casting, after placing of the rebar cage.
 9. The self-launchingmovable scaffolding system according to claim 1 further comprising frontsupport main jacks which are activated to transfer load from the maingirder to the front support during casting.
 10. The self-launchingmovable scaffolding system according to claim 1 further comprising frontsupport legs which provide a transfer of load further to a columnfooting.
 11. The self-launching movable scaffolding system according toclaim 1 further comprising front support side shifting cylinders whichare equipped at a top of the front support and the main girder in orderto allow transverse adjusting of the main girder.
 12. The self-launchingmovable scaffolding system according to claim 1 further comprising amono-rail which is set along the rear nose, the main girder, the frontnose and an electrical lifting hoist.